The addition of pyrite to a coal liquefaction process to improve conversion of normally solid dissolved coal to liquid coal and gaseous hydrocarbons is described in U.S. Pat. Nos. 4,222,847 and 4,222,848 to N. L. Carr and B. K. Schmid. The patents demonstrate that the addition of increased amounts of pyrite of reduced size to a coal liquefaction process which employs recycle of a product slurry correspondingly increases the yield of C.sub.5 --900.degree. F. (482.degree. C.) liquid, while decreasing the yield of normally solid dissolved coal 900.degree. F.+ (482.degree. C.+) product.
Although pyrite is a useful catalytic material in such systems, the addition of pyrite to the feed slurry adds to the pumpability problem normally associated with pumping slurries. Moreover, pyrite is a potential pollutant since it contains sulfur and can cause a disposal problem as it is withdrawn from the system as slag in potentially large quantities. Thus, it would be highly desirable to minimize the amount of pyrite added to a coal liquefaction process, particularly when the process will be conducted on a large scale basis, so as to reduce the total solids to be pumped and to be disposed of.